Batteries (cells) that generate electric power through physical or chemical reaction to supply the generated power to the outside are used when AC power to be supplied to the building is not obtained, or DC power is required according to the living environments surrounded by various electric and electronic devices.
Among such batteries, primary batteries and secondary batteries, which are chemical batteries using chemical reaction, are generally used. The primary batteries are consumable cells which are collectively referred to as dry cells. Also, secondary batteries are rechargeable batteries that are manufactured by using a material in a redox process between current and a substance is repeatable several times. When the reduction reaction is performed on the material by the current, power is charged, and when the oxidation reaction is performed on the material, power is discharged. Such the charging-discharging is repeatedly performed to generate electricity.
A lithium ion battery of the secondary batteries is manufactured through the following processes. An active material is applied to each of a positive electrode conductive foil and a negative electrode conductive foil at a predetermined thickness, and a separator is disposed between the positive electrode conductive foil and the negative electrode conductive foil, and then, an electrode assembly, in which the positive electrode conductive foil, the separator, and the negative electrode conductive foil are wound several times in a jelly-roll or cylindrical shape, is accommodated into a cylindrical or prismatic can, a pouch, and the like to seal the resultant product, thereby manufacturing the lithium ion battery.
A case of a lithium ion battery according to the related art is disclosed in Korean Patent Publication No. 10-1997-0054691.
The case of the lithium ion battery according to the related art includes a vent in a bottom surface of a can to discharge a gas when an internal pressure increases.
However, a pre-plated nickel (Ni) layer of the can may be damaged by punching that is introduced for forming the vent.
Also, when a negative electrode tab is welded, a portion of the tab may be bent. Also, when the bent tab comes into contact with the vent, the nickel layer may be additionally lost to accelerate corrosion within the can due to the resistance current applied during the welding.